甘蔗健康种子发芽率影响因素分析

该研究主要通过温室沙培试验,分析了甘蔗健康种子单芽材料各因素(单芽长度、不同芽位、泡水时间)及甘蔗基因型、种衣剂及保存天数三种因素对甘蔗健康种子发芽率的影响。结果表明:不同浸泡时间、不同单芽长度和芽位对健康种子单芽发芽率的影响极显著。随着单芽长度的增加,发芽率有明显的提高;随着泡水时间的增加,发芽率不断降低,但各处理之间差异不显著;顶部芽位的发芽率较高,但其他芽位之间发芽率的差异不明显。甘蔗健康种子发芽率具有明显的基因型差异,其中GT28和ROC22的发芽率较高,发芽率在70%左右。种衣剂包衣处可显著提高甘蔗健康种子的发芽率,与其他种衣剂相比扑力猛包衣处理的甘蔗健康种子发芽率最高,且差异显著。随着保存天数的增加,甘蔗健康种子的发芽率不断下降,且差异显著,当保存时间超过8 d时,发芽率低于60%。     

Ammonium heptamolybdate,an inhibitor of plant invertases

Ammonium heptamolybdate was an inhibitor of plant invertases. The inhibition was a linear mixed type and the constants K_i and aK_i were determined. α- and β-glycerophosphate, 2,3-diphosphoglycerate, glucose-1-phosphate, phosphoenolpyruvate, pyruvate and malate suppressed the inhibition. The curves of enzyme recovery against the concentrations of these activators were sigmoid. UV spectrophotometry showed complex formation between inhibitor and each activator, and indicated that sucrose did not form a complex with the inhibitor. Consequently, heptamolybdate is postulated to act by a reversible binding to the enzyme.     

Molasses supplementation promotes conidiation but suppresses aflatoxin production by small sclerotial Aspergillus flavus

AIMS: To find a supplemental ingredient that can be added to routinely used growth media to increase conidial production and decrease aflatoxin biosynthesis in small sclerotial (S strain) isolates of Aspergillus flavus. METHODS AND RESULTS: Molasses was added to three commonly used culture media: coconut agar (CAM), potato dextrose agar (PDA), and vegetable juice agar (V8) and production of conidia, sclerotia, and aflatoxins by A. flavus isolate CA43 was determined. The effect of nitrogen sources in molasses medium (MM) on production of conidia, sclerotia and aflatoxins was examined. Water activity and medium pH were also measured. Conidia harvested from agar plates were counted using a haemocytometer. Sclerotia were weighed after drying at 45 degrees C for 5 days. Aflatoxins B(1) and B(2) were quantified by high-performance liquid chromatography. Addition of molasses to the media did not change water activity or the pH significantly. Supplementing CAM and PDA with molasses increased conidial production and decreased aflatoxins. Two-fold increased yield of conidia was found on MM, which, like V8, did not support aflatoxin production. Adding ammonium to MM significantly increased the production of sclerotia and aflatoxins, but slightly decreased conidial production. Adding urea to MM significantly increased the production of conidia, sclerotia and aflatoxins. CONCLUSIONS: Molasses stimulated conidial production and inhibited aflatoxin production. Its effect on sclerotial production was medium-dependent. Water activity and medium pH were not related to changes in conidial, sclerotial or aflatoxin production. Medium containing molasses alone or molasses plus V8 juice were ideal for conidial production by S strain A. flavus. SIGNIFICANCE AND IMPACT OF THE STUDY: Insight into molecular events associated with the utilization of molasses may help to elucidate the mechanism(s) that decreases aflatoxin biosynthesis. Targeting genetic parameters in S strain A. flavus isolates may reduce aflatoxin contamination of crops by reducing the survival and toxigenicity of these strains.     

Fattening Pelibuey lambs with sugar cane tops and corn complemented with or without slow intake urea supplement

One hundred and eighty Pelibuey lambs were fattened for 120 days with three treatments evaluating in situ DM disappearance, voluntary DM or OM intake, rumen degradation, rate of passage, NH₃ and VFA concentration, apparent digestibility, ruminal pH, total fermentable carbohydrates and weight gains. The first diet (T1), 60 lambs (25.7 ± 0.7 kg BW) plus two cannulated sheep were fed 100% sugar cane tops (SCT) per day; treatment 2 (T2), 60 lambs (25.4 ± 0.4 kg BW) plus two cannulated sheep diet was SCT supplemented with 200 g DM of slow intake urea supplement (SIUS) (a 4% urea mixture) per day. Treatment 3 (T3), 60 sheep (25.5 + 0.5 kg BW) plus two cannulated animals, fed SCT and corn crop chopped (C) mixture (40:60%) were supplemented with 200 g SIUS per day. Ruminal kinetics were determined thereafter in four adult ruminal cannulated sheep in metabolic cages. A 100% corn diet was added to the second trial (T4). At all times, fibrous forages were available and exceeded VDMI. Daily BW gain by SCT animals was 70 g/d compared to 135 g/d for SCT/SIUS and 218 g/d for SCT/C/SIUS diets (P < 0.05). Total forage intake was similar for T1 and T2 treatments and higher for T3 (P < 0.05). Kinetics observation showed a total DMI variation increasing from 474 g/d for T1; 597 g/d for T4 to 797 g/d for T2, and 917 g/d for T3, being different for the last two treatments compared with the first two (P < 0.001) and similar among SIUS diets. Rumen pH diminished from 6.8 to 6.7 at 2 h, when SIUS was offered, and stayed above 6.5 during the 12 h of sampling when SIUS was the only supplement and 6.3 when corn was added, while in SCT lambs, ruminal pH decreased to 6.2 by 6 h and rose again to 6.4 after 12 h favoring bacterial multiplication. Ammonia concentration and digestion of potential digestible and indigestible fractions were significantly augmented (P < 0.05) by SIUS. In vivo nitrogen digestibility was different (P < 0.05) among diets: T1, T2, T3, and T4 (36.5%, 74.1%, 76.5%, and 39.4%, respectively). In vivo digestibility of DM, OM, cellulose and hemicellulose was similar among T2 and T3 groups but different when T1 or T4 diets were offered (P < 0.05). NDF digestibility was higher for T3 (77.1%) and T2 (75.1%) but different from T1 (57.1%) and T4 (59.1%) (P < 0.01). In situ DM disappearance did not show differences among T2 and T3 diets at 9, 12, 24 and 48 h of incubation but differed in percentage for T1 and T4. Digestion rate constant (k_d) was similar among SIUS diets 0.038 and 0.039, but different from T1 and T4 diets 0.023; 0.021 (P < 0.05). True digestibility of NDF was higher (P < 0.05) in SCT/SIUS/C (32.5%) and SCT/SIUS (32.7%) compared with SCT (26.2%) and C (27.4%). Passage of NDF was different (P < 0.05) between T1 (0.059 h⁻¹) and T4 (0.061 h⁻¹) from 0.079 (T2) and 0.081 k_p/h (T3). The half-time (t_1/2) disappearance for hemicellulose was higher (P < 0.05) for SCT/SIUS (22.1 h) and SCT/SIUS/C (29.2 h) as compared to SCT (18.1 h). Kinetic performance among SCT and C diet did not have a statistical difference. Utilization of fibrous forages by lambs was higher (P < 0.05) for SIUS diets. VDMI and apparent digestibility showed better performance for DM and OM, lower acetate molar proportions and greater feed intake by both SIUS diets which was reflected in body weight gain.     

Impact of the arundo wasp,Tetramesa romana (Hymenoptera: Eurytomidae), on biomass of the invasive weed,Arundo donax (Poaceae: Arundinoideae), and on revegetation of riparian habitat along the Rio Grande in Texas

An invasive grass, Arundo donax, occupies thousands of hectares of arid riparian habitat along the Rio Grande in Texas and Mexico, and has negative impacts on national security, water resources, and riparian ecosystems. The shoot-tip-galling wasp Tetramesa romana was released in 2009 between Brownsville and Del Rio, Texas, and has dispersed over 800?km along the river channel. Plots along the river were surveyed for shoot counts of arundo and all other plant species in 2016 at seven sites in regions in which prior studies had documented a 22% decline in arundo biomass (estimated from live shoot length) from 2007 to 2014. Estimated live biomass declined a further 32% between 2014 and 2016. Native plants accounted for 86% of the 44 species encountered in plots. Individual plots averaged five plant species, and arundo was most abundant in only 9 of 21 plots. Arundo live biomass and shoot density were negatively associated with plant diversity, indicating that live arundo interferes with germination and/or survival of other plant species. The proportion of dead shoots in plots, proportion of wasp-galled shoots, and density of exit holes made by emerging adult wasps per metre live main shoot length were positively associated with plant diversity in a combined model. Regressions indicated that the effects of wasp damage measures on diversity were mediated through their effects on main shoot mortality. By reducing live arundo biomass, the arundo wasp is fostering recovery of native plant communities at riparian sites along the Rio Grande.     

不溶性着色蔗渣木聚糖检测木聚糖酶活性*

蔗渣木聚糖经1.4-丁二醇二环氧甘油醚与染料气巴蓝3GA交联形成不溶性着色固体。这种着色蔗渣木聚糖在pH4-8范围内表现稳定,用于评价木聚糖酶活性及在平板上检测产酶微生物具有简捷而灵敏的效果。     

Distribution of Vascular Tissue in Four Rattan Canes

Vascular bundle density, fibre proportion, size of vascular bundle and diameter of metaxylem vessel in canes of four rattans, i.e. Daemonorops margaritae, Calamus simplicifolius, C. tetradactylus and C. dioicus, were measured in relation to their radial positions of cross section and different cane heights. The radial and vertical distributions were expressed by 1 ×1 mm of unit, denominated 'a layer', from the bark to centre and by the number of nodes from the base to top respectively. All the measurements were done with a micro-projector. Distribution of radial direction. At all cant' heights, a distinct or even abrupt change in the measured characteristics occurs between the peripheral two layers. From this zone towards the centre, the vascular bundle density shows approximately the same in all inner layers; the fibre proportion demonstrates a decreasing tendency; the size of vascular bundle and the diameter of metaxylem vessel reveal an increasing trend at different degree. Distribution of vertical direction. The vascular bundle density in the various layers shows a little or even no difference between different heights. The fibre proportion in the outermost layer exhibits a decreasing tendency' from the base to top, and in inner layers some of them still have more or less the similar tendency. There are obvious differences, but noany pattern of variation, between the different heights in relation to both size of vascular bundle and diameter of metaxylem vessel in all the layers, except that the later in C. dioicus and D. margaritae shows an increasing trend from the base to top. In addition, the practical significance of the distribution of fibre proportion was discussed.     

重组大肠杆菌利用蔗糖及糖蜜发酵生产丁二酸

富含蔗糖的甘蔗糖蜜可作为制备丁二酸的廉价原料。然而生产丁二酸的潜力菌株大肠杆菌Escherichia coli AFP111不能代谢蔗糖。为了使其具有蔗糖代谢能力,将E.coli W中非PTS蔗糖利用系统蔗糖通透酶的编码基因csc B,果糖激酶的编码基因csc K和蔗糖水解酶的编码基因csc A克隆并表达到AFP111中,获得重组菌株AFP111/p MD19T-csc BKA。经厌氧发酵验证,重组菌株72 h消耗20 g/L蔗糖,丁二酸产量达到12 g/L。在3L发酵罐中采用有氧阶段培养菌体、厌氧阶段发酵的两阶段发酵方式,厌氧发酵30 h,重组菌株以蔗糖和糖蜜为碳源丁二酸产量分别为34 g/L和30 g/L。结果表明,通过外源引入非PTS蔗糖利用系统,重组菌株具有较强的代谢蔗糖生长及合成丁二酸的能力,并且能够利用廉价糖蜜发酵制备丁二酸。     

用GGE双标图分析甘蔗品种性状稳定性及试点代表性

算术平均法经常被用于评估甘蔗品种产量的稳定性和适应性,并用方差分析来估计区域试验的试验误差.然而,地点和年份的差异使品种的差异难以得到准确评估.为客观评价甘蔗品种的稳定性和适应性,本研究采用GGE双标图对2008-2009年我国甘蔗区域试验5个试点中的7个甘蔗品种试验数据进行分析.结果表明:福农30号为蔗茎产量高且稳产性高的品种,粤甘18号为含糖量高且性状稳定的品种,福农28号和云蔗99-91为高蔗糖分且性状稳定的品种,粤甘16号的蔗茎产量和含糖量最高,但稳定性一般;在各试点中,福建漳州和广东遂溪的代表性和鉴别力较强.GGE双标图分析为客观评价甘蔗参试品种的丰产性和稳定性提供了直观、有效的手段,为甘蔗新品种的鉴定与推广提供了科学依据.